During the use of contact lenses, the lenses become contaminated and the accumulation of pathogenic germs must not be permitted to exceed a critical limit in order to avoid the danger of an infection of the eye. For this reason, a daily disinfection of contact lenses is necessary. This is primarily true for hydrophilic soft lenses, which are used widely today.
For this purpose, a method is known which utilizes hydrogen peroxide, which has both an oxidizing, germ-killing, cleaning effect and an odor-killing effect. In this method, the contact lenses are first exposed to the action of a 3 to 30 percent solution of hydrogen peroxide, which can for example take place in a small container in which the contact lenses are arranged in a carrying basket. The time period during which the hydrogen peroxide must act onto the contact lenses in order to achieve a sufficient disinfection and cleaning is approximately 20 minutes. The residual hydrogen peroxide which adheres to the contact lenses must subsequently be removed, and in the known method this is done by moving the contact lenses into a second container which contains a neutral liquid and a catalyst, in the presence of which catalyst the hydrogen peroxide is split up into water and oxygen according to the formula: EQU 2 H.sub.2 O.sub.2 .fwdarw.2 H.sub.2 O+O.sub.2
The catalyst is a metal-coated solid body.
A disadvantage of the conventional method is that the second method step, namely the decomposition of the hydrogen peroxide, takes a relatively long time. At least four hours are typically needed for this. If, for example, a user of contact lenses forgets in the evening to change the contact lenses from the hydrogen peroxide solution to the solution containing the catalyst, there is usually insufficient time the next morning to remove the hydrogen peroxide residues from the contact lenses and thereby avoid a burning sensation in the eyes during wearing of the contact lenses. According to a modification of the known method, the metallic catalyst is already present in the hydrogen peroxide solution during the time when the hydrogen peroxide solution acts onto the contact lenses. Thus, the disinfecting and cleaning operation of the contact lenses and the decomposition of the hydrogen peroxide by the catalyst start at the same time. This is possible in the known method, since the decomposition which is effected by the catalyst takes place slowly. This one-step method also has the important disadvantage that it is very slow (it takes several hours). Moreover, in this known method, remaining residues of hydrogen peroxide are thereafter removed by a final washing of the lenses in a salt solution.
A basic purpose of the invention is to improve the method mentioned above so that the time span required for the second method step is substantially reduced and at the same time a very high-grade removal of the hydrogen peroxide is achieved.
The foregoing purpose is met by a method of the type set forth above in which the catalyst is catalase.
In one development of the invention, catalase is added, after the first time interval has elapsed, to the hydrogen peroxide solution in which the hygienic article is immersed.
In another development of the invention, the hydrogen peroxide solution is replaced with, or the hygienic article is moved to, a neutral liquid which contains catalase or to which catalase is subsequently added. The neutral liquid is preferably a sodium chloride solution. Catalase is added to the neutral liquid either in the form of tablets or in the form of a highly concentrated solution.